Goi's Fitness Forum

Comparison of weight-loss diets with different compositions of fat, protein, and carbohydrates

BACKGROUND: The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year.

METHODS: We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content.

RESULTS: At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels.

CONCLUSIONS: Reduced-calorie diets result in clinically meaningful weight loss regardless of which macronutrients they emphasize.

This paper was so poorly designed and executed it's not even funny...

(From Feb 09 Issue of Alan Aragon's Research Review)

Comparison of Weight-Loss Diets with Different
Compositions of Fat, Protein, and Carbohydrates.

Sacks FM, et al. N Engl J Med. 2009 Feb 26;360(9): 859-73.
[NEJM]

PURPOSE: The possible advantage for weight loss of a diet that
emphasizes protein, fat, or carbohydrates has not been
established, and there are few studies that extend beyond 1 year.
METHODS: We randomly assigned 811 overweight adults to
one of four diets; the targeted percentages of energy derived
from fat, protein, and carbohydrates in the four diets were 20, 15,
and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and
35%. The diets consisted of similar foods and met guidelines for
cardiovascular health. The participants were offered group and
individual instructional sessions for 2 years. The primary
outcome was the change in body weight after 2 years in two-by-
two factorial comparisons of low fat versus high fat and average
protein versus high protein and in the comparison of highest and
lowest carbohydrate content. RESULTS: At 6 months,
participants assigned to each diet had lost an average of 6 kg,
which represented 7% of their initial weight; they began to
regain weight after 12 months. By 2 years, weight loss remained
similar in those who were assigned to a diet with 15% protein
and those assigned to a diet with 25% protein (3.0 and 3.6 kg,
respectively); in those assigned to a diet with 20% fat and those
assigned to a diet with 40% fat (3.3 kg for both groups); and in
those assigned to a diet with 65% carbohydrates and those
assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg,
respectively) (P>0.20 for all comparisons). Among the 80% of
participants who completed the trial, the average weight loss was
4 kg; 14 to 15% of the participants had a reduction of at least
10% of their initial body weight. Satiety, hunger, satisfaction
with the diet, and attendance at group sessions were similar for
all diets; attendance was strongly associated with weight loss
(0.2 kg per session attended). The diets improved lipid-related
risk factors and fasting insulin levels. CONCLUSION:
Reduced-calorie diets result in clinically meaningful weight loss
regardless of which macronutrients they emphasize.
SPONSORSHIP: National Heart, Lung, and Blood Institute and
the General Clinical Research Center, National Institutes of
Health.

Study strengths

Compared to most dietary interventions, this one had a large
randomized sample; 811 subjects were recruited, 645 (80%)
completed the study. It was also exceptionally long, spanning
over 2 years (October 2004 through December 2007). Blinding
was facilitated in part by the use of similar foods for each diet.
Although the diets were not provided by the lab, group sessions
were held once a week, 3 of every 4 weeks during the first 6
months and 2 of every 4 weeks from 6 months to 2 years.
Individual sessions were held every 8 weeks for the entire 2
years. Daily meal plans in 2-week blocks were provided.
Subjects recorded their intake in a daily food diary as well as a
web-based self-monitoring tool that calculated how closely their
daily food intake met the goals for macronutrients and energy.
Behavioral counseling was integrated into the group and
individual sessions to promote adherence to the assigned diets.

Study limitations

Although the 4 diets allowed for a dose-response test of
carbohydrate intake ranging from 35-65% of total kcals, most
low-carb dieters wouldn’t consider 35% accurately
representative of the low end, which commonly falls in the
neighborhood of 15-20%. As well, protein hovered within a
curiously low range of 15-25%. The targeted caloric deficit was
750 kcal less than baseline intake. Since baseline intake
averaged 1966 kcal, a 750 kcal reduction equals 1216 kcal. A
protein intake range of 15-25% of this figure ends up being a
paltry 45.6-76 g. Targets aside, the actual caloric intake range at
the 2-year point was 1413-1560 kcal, and protein intake ranged
from 19.6-35.1% (73-126g). This ended up being a little more
sensible, particularly from the standpoint of preserving lean
mass under hypocaloric conditions. This brings up the next
limitation, which was a lack of measurement of body
composition. However, this shortcoming was partially alleviated
by measuring waist circumference. Although exercise was by an
online self-monitoring tool and questionnaire, the goal of 90
minutes of moderate physical activity per week clearly is not
applicable to athletic populations.

Comment/application

The main finding is that the diets were equally successful in
promoting clinically meaningful weight loss and weight loss
maintenance over the 2-year trial duration. Satiety, hunger, and
satisfaction with the diet were similar for all diets. This isn’t too
surprising given the non-extreme hypocaloric intake coupled
with the (relative) lack of disparity in the lowest and highest
intakes of carbohydrate and protein. As expected, all participants
had difficulty achieving the goals for macronutrient intake of
their assigned group despite the intensive behavioral counseling.

The importance of in-person/group dietary counseling was
highlighted in this trial. Interestingly, the importance varied
across groups. Subjects assigned to the lower-protein or higher-
fat diet did not have to drastically change their customary level
of dietary protein and fat. Therefore, they had to focus primarily
on reducing overall intake. In contrast, the participants in the
higher-protein or lower-fat groups had the dual challenge of
changing their habitual diet composition in addition to reducing
intake. The investigators were not surprised that attendance at
group counseling sessions was strongly related to adherence to
high-protein or low-fat goals, but not strongly related to the goals
in the average-protein or high-fat groups.

I recently pop-quizzed a group of students and asked them
what’s the best diet (I gave them a few choices that covered the
range of pyramid-type to Atkins-type diets), and had then
discuss things amongst themselves. None of them got it. The
answer to the trick question was: the best diet is the one you can
adhere to. In agreement with this philosophy, the authors of the
present trial conclude that calorie reduction – however it’s best
achieved by the individual – is more important for long-term
weight loss than specific proportions of the macronutrients. Bear
in mind that this is particularly true with non-athletic populations
with more general weight loss goals. Sports with varying energy
demands will undoubtedly vary in respective nutritional support.

More commentary here, hereand here.